Conventional thin-film light emitting devices are commonly formed on a wafer, diced/singulated into individual dies, and mounted on a submount structure. The submount provides the support required to support the individual dies, and the electrical circuitry that allows an external power source to be coupled to the light emitting dies. The submount structure is generally configured to host multiple light emitting devices, to provide for efficient additional processing, such as phosphor coating and encapsulation. The submount structure is subsequently sliced/diced to provide individual (singulated) light emitting devices that can be placed in lamps, attached to printed circuit boards, and so on.
The singulated light emitting devices may include multiple light emitting elements, to increase luminance, to produce a composite of multiple colors, and so on. The increasing size and complexity of such devices has led to the development of chip-scale fabrication techniques, wherein the semiconductor chip forming the light emitting device includes the circuitry required to interconnect the multiple elements, as well as providing external connections to these elements, thereby simplifying the features that may need to be included in the submount.
The use of a submount requires that the individual dies be singulated from the wafer, picked and placed accurately upon the submount, then affixed to the submount structure, typically via soldering. The operations that can be performed on the dies while still on the wafer may be limited due to the processes involved with affixing the individual dies on the submount structure.
Additionally, the singulation of the light emitting devices from the submount structure may be hampered by the structural support provided by the submount. The slicing apparatus must be able to cut through the submount, and a submount that is sufficiently thick and/or rigid to structurally support a group of light emitting devices through the additional processes is more difficult to slice than a non-structural support.